1. Field of the Invention
The invention is in the field of electronics.
2. Related Art
Sigma-delta modulators are commonly used to generate pulses whose summed area is representative of an input signal. The generated pulses may vary in their width or their separation. Sigma-delta modulators are found in a wide variety of electronic components including analog-to-digital (ADC) converters, digital-to-analog (DAC) converters, frequency synthesizers, switched-mode power supplies, switched amplifiers and motor controls.
FIG. 1 illustrates an example of a second order sigma-delta modulator 100. This module includes a Combiner 105 configured to combine an input signal A and a feedback signal F. The combined signals A and F are integrated by a first Integrator 110 to produce an output B. A Combiner 115 is used to combine the output B and the feedback signal F. The combined signals B and F are then integrated using a second Integrator 120 to produce an output C, which is quantized using a Quantizer 125 to produce a final output D. The output is provided to a Feedback Generator 130 to generate the feedback signal F. The feedback signal is configured to reduce noise introduced by the integration and quantization.
Sigma-delta modulators of first order, third order or higher order are known in the prior art. In a first order sigma-delta modulator the Combiner 115 and Integrator 120 would be omitted, while in a third order modulator an additional Combiner 115 and Integrator 120 would be included. An advantage of higher order is that each stage of Combiner 115 and Integrator 120 servers to further reduce noise in the frequency band of interest. A disadvantage of higher orders is that then number of bits required to represent the integrated signals (e.g., signals B and C) is greater at each stage. This increases the complexity and time required to perform the signal combinations at each subsequent combiner, e.g., Combiner 115.